FR3007179A1 - METHOD AND SYSTEM FOR AIDING THE AIRCRAFT OF AN AIRCRAFT - Google Patents

Abstract

The runway condition determined by an aircraft on the ground and provided to the aircraft on approach is not sufficient to account for any runway degradation that has occurred since the previous determination of this runway condition. The invention provides for determining a local information function of a local runway condition when the aircraft is taxiing on the runway in order to update in real time or near real-time data used by a brake assist system, according to that the local track condition associated with the determined local information informs a track degradation with respect to a reference track condition initially used.

Description

FIELD OF THE INVENTION The present invention relates to a method and a system for aiding the piloting of an aircraft, and to an aircraft equipped with such a system.

BACKGROUND OF THE INVENTION During the landing and takeoff phases, and more generally the taxiing of an aircraft, knowledge of the surface state of the runway is of paramount importance. Indeed, this knowledge depends on the braking performance prediction of the aircraft. It is thus possible: - to estimate as best as possible the distance necessary to stop the aircraft during its landing in the interests of safety, - not to overestimate this stopping distance necessary to immobilize the aircraft and therefore not to penalize, beyond measure, the use of the runway and the aircraft. Many flight control systems require the knowledge of this runway state precisely. For example, the documents FR2817979 and FR2857468 provide piloting assistance devices during the approach and landing phases, known as Brake-To-Vacate (BTV), for monitoring and controlling the braking of the aircraft through closed-loop control laws. These control laws depend directly on the estimation of stopping distances from the track condition. On the other hand, the documents FR2936077 and FR2914097 provide piloting assistance devices during the approach and landing phases, known as Runway Overrun Protection (ROP) or Runway Overrun Warning (ROW), allowing to detect a risk of runway departure depending on the runway condition, in order to alert the pilot either to induce him to turn on the throttle or to trigger maximum braking.

However, the braking performance of an aircraft on a so-called contaminated track and therefore the necessary stopping distance are difficult to predict because of the difficulty in knowing reliably and accurately the track condition, determining in the deceleration of the aircraft. Traditionally, runway conditions are determined by ground personnel, or evaluated by a pilot on landing and reported in a landing report.

This runway status information, transmitted to the approaching aircraft, is however unreliable and possibly out of date rather quickly. Indeed, the track condition characteristics are of high volatility over time. In order to make reliable the estimation of a runway condition, the documents FR2930669 and FR2978736 propose solutions making it possible to automatically estimate the state of the runway from the measured braking performance of an aircraft during its landing, and this regardless of the type of aircraft. However, the track condition thus determined and provided to the aircraft on approach does not make it possible to account for a possible degradation of the runway occurring between the two landings. The present invention aims to improve the flight control assistance of an aircraft especially during the landing phase to take account of this possible runway degradation.

SUMMARY OF THE INVENTION To this end, the invention aims in particular at a method of assisting the piloting of an aircraft during the landing phase, comprising a step of generating a braking data, typically a predictive stopping distance. , as a function of a reference track state, said braking data being supplied at the input of a brake assist module, the method being characterized by the following steps: determining a local information function of a local runway condition at the aircraft during landing; and updating the reference runway state or braking data according to the determined local information, when the local information indicates a local track condition that is more degraded than the runway condition of the runway. reference, so as to provide updated braking data at the input of the brake assist module. Correlatively, the invention also provides a system for assisting the piloting of an aircraft in the landing phase, comprising: a module for generating a braking data as a function of a reference track state; a brake assist module receiving as input said braking data generated; a module for determining a local information function of a local runway condition at the aircraft during landing; and a module for updating the reference track state or the braking data as a function of the determined local information, when the local information indicates a local track condition that is more degraded than the state reference track, so as to provide updated braking data at the input of the brake assist module. Thus, information relating to the runway condition is updated during the landing phase, which makes it possible to account for a possible degradation of the runway since the determination of the runway condition. reference, for example by the aircraft having previously landed, and to control accordingly the aircraft. For this purpose, in addition to obtaining the reference runway status by the flight control system as in the prior art, another information function of the local runway condition to the aircraft during the landing is determined in order to deduce a possible runway degradation from the reference runway condition used to control the braking. This local runway condition characterizes the runway area on which the aircraft is taxiing during landing. When the local information reveals a degradation of the runway state with respect to the reference runway condition, data operated by the system to control the braking is updated in real time during the landing, including reference track condition, ie a braking data internal to the system, which makes it possible to adjust the braking of the aircraft to the extent of the degradation of the track undergone. The braking performance and therefore the safety of the aircraft during landing are therefore improved.

The piloting aid system has advantages similar to the method according to the invention. Other features of the method and the piloting aid system according to different embodiments are described in the dependent claims. In a particular embodiment, the method comprises a step of reconfiguring a brake assist system of the aircraft, manipulating the reference runway condition or the braking data, depending on the runway condition. reference or braking data updated. In a first embodiment of the invention, the local information is representative of a current level of braking or deceleration of said aircraft, and the method comprises a step of obtaining a so-called reference information representative of a braking or deceleration level of said aircraft derived from the reference runway condition or brake data, and a step of comparing the reference information with the local information to determine if the local runway condition is more degraded than the reference runway state. This reference information may correspond to an estimate of a theoretical braking or deceleration level calculated by the system as a function of the reference track condition. Similarly, the local information may correspond to an effective value of a braking or deceleration level of the aircraft, for example measured by on-board sensors.

In a second embodiment of the invention, the local information is an estimate of the local runway condition by a system embedded in the aircraft, and the updating step updates the runway state. reference by the estimated local runway condition. In particular, in this second mode, the estimation of the local track state can be deduced from measurements by sensors. In a particular embodiment of the invention, the update step is performed when at least one of the following critical conditions is encountered: the difference between a commanded deceleration value of the aircraft and a measured deceleration value by the aircraft exceeds a predetermined threshold; the level of manual depression of a brake pedal by an operator exceeds a predetermined threshold; the difference between a controlled braking level of the aircraft and a measured braking level in the aircraft exceeds a predetermined threshold; an anti-skid system of the aircraft is triggered. Correlatively, the aforementioned system may comprise a module for determining whether at least one of the following critical conditions is encountered in order to trigger an update by the update module: the difference between a commanded deceleration value of the aircraft and a deceleration value measured by the aircraft exceeds a predetermined threshold; the level of manual depression of a brake pedal by an operator exceeds a predetermined threshold; the difference between a commanded braking level of the aircraft and a measured braking level in the aircraft exceeds a predetermined threshold; an anti-skid system of the aircraft is triggered. The flight aid system thus calculates braking instructions adapted in real time to the actual landing conditions, thus improving the safety of the latter.

In a particular embodiment of the invention when reference information is the reference track state, the updating step includes replacing the reference information with the local information. For example, the reference runway condition is received from a previously landed aircraft or from a ground station, and the update makes it possible to replace this reference runway condition with a local runway condition determined by a embedded system of the aircraft, more representative of the actual conditions of the runway. The system can then calculate a new braking or warning setpoint based on the reference information (track status) thus updated. This new braking or warning setpoint is then better adapted to the actual conditions of the track. In another particular embodiment of the invention, the update step comprises the calculation of a correction coefficient dependent on the determined local information and the correction of the braking data, typically a predictive distance value. stop used to calculate the braking setpoint or warning, based on the calculated correction factor. In another particular embodiment of the invention, the braking data is a minimum stopping distance that is a function of the reference track state, and the updating step includes the correction of the minimum distance of stopping from the determined local information, by interpolation of several minimum stopping distances associated respectively with theoretical track states. In particular, the determined local information can be representative of a current level of braking or deceleration of said aircraft, and the correction of the minimum stopping distance from the determined local information can then include the interpolation of minimum distances. stoppages associated with theoretical braking or deceleration levels as a function of the determined current braking or deceleration level. The invention also relates to an aircraft comprising at least one flight control system as defined above. It is thus adapted to implement the above-mentioned driving aid method. BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will become apparent in the following description, illustrated by the accompanying drawings, in which: FIG. 1 illustrates a system for aiding the piloting of an aircraft according to particular embodiments of the invention; FIG. 2 represents, in the form of a logic diagram, the main steps of a method of assisting the piloting of an aircraft according to the invention; FIGS. 3, 4a and 4b represent, in the form of logic diagrams, the steps of methods of assisting the piloting of an aircraft according to three embodiments of the invention; and - Figure 5 illustrates an operational scenario of a landing during which the invention is used.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 diagrammatically represents a system 1 for aiding the piloting of an aircraft, in accordance with a particular embodiment of the invention. The system 1 comprises a braking assistance system 10 which, from a reference track state EP, for example received from a previously landed aircraft or from a ground station, generates a setpoint C (EP ) of braking provided at the input of a braking device of the aircraft or generates a warning message C (EP) provided at the input of a device for restitution of the aircraft. Note that the alert message may be a non-alert message at the beginning of the landing.

The braking assistance system 10 comprises a module 11 for generating a braking data as a function of the reference track state EP and comprises a braking assistance module 12 configured to generate the setpoint C (EP). from the braking data generated. In the example of the figure, the braking data generation module 11 is a stopping distance estimator configured to estimate a predictive stopping distance D (EP) of the aircraft as a function of the state. reference track EP, and possibly other parameters of the aircraft (such as its speed, weight, braking capacity, etc.). The EP track condition is generally based on models prescribed by regulations, for example the following states in increasing order of degradation: DRY (for dry track), WET (for wet track), COMPACTED SNOW, WATER or SLUSH (for runways contaminated with standing water or slush), and ICY (for ice). The brake assist system 10 may for example be a Brake-To-Vacate (BTV) type device as described in the documents FR2817979 and FR2857468 allowing the pilot to control the braking of the aircraft according to a theoretical stopping distance associated with the reference track state EP. The braking setpoint C (EP) generated by the device BTV thus controls a braking device, for example brakes.

This braking setpoint C (EP) may for example represent a braking command imposing a certain deceleration corresponding to the predictive stopping distance D (EP) for the aircraft. As a variant, the braking assistance system 10 may be an alert and runway overrun risk management device of the Runway Overrun Protection (ROP) type as described for example in the documents FR2936077 and FR2914097. The ROP adjusts the predictive stopping distance at the output of the stopping distance estimator according to the input reference track state, and therefore, if certain conditions are met (for example, if the predictive distance 15 stops the aircraft near the end of the runway or outside thereof), can issue alerts and / or braking orders. These alerts may consist of visual or sound messages displayed or broadcast in the cockpit of the aircraft, for the attention of the crew. A braking command may be an automatic (full pressure) maximum braking command for the braking device. The system 1 also comprises a local information determination module ibc which is a function of a local runway condition at the aircraft, that is to say the state of the runway where the aircraft rolls during the flight. 'landing. This determination is for example made from so-called local measurements in the sense that at least one physical quantity of the aircraft is measured during the landing at the moment when the aircraft is rolling in the part of the runway considered as "local". For this, the aircraft is equipped with ad hoc sensors for example located at each wheel to determine for example the vertical load applied to them and / or the braking torque applied by the braking system, or the speed rotation of the wheels during landing. The aircraft can also comprise one or more ADIRS ("Air Data Inertial Reference System") inertial units for obtaining aircraft ground speed, position, acceleration and temperature measurements, a system of aircraft data, and flight management system (FMS), equipment for estimating the physical size of tires (temperature and internal pressure), and a GPS module providing the position of the aircraft. Another physical quantity that can be measured is the level of depression of the brake pedals by the pilot or a brake pressure.

In general, a lot of data can be provided and used to determine the local information. As an illustration, the module 20 receives the location of the center of gravity CG of the aircraft, the slope of the runway, the outside temperature, data of wind (force and direction), velocities (on the ground, true and calibrated aerodynamics, wheels), altitude data (pressure, ...), aircraft mass, airport data, track data used including GPS track coordinates, aircraft GPS position data, engine driving parameters, brake pedal depressing information, moving surface conditions (such as high lift devices) , the elevator, the air brakes, the fins), measurement information relating to the tires (internal temperature and pressure), representative Boolean information, for example the touch of the main gear on the track and the opening of the engine back-thrust doors, etc. It is noted that all or part of these data, mainly those relating to dynamic data of the aircraft or external conditions for example, can be updated in a function of time, in particular during the running of the aircraft: speeds, engine thrust levels, wind, temperature and tire pressure, etc. The measured data can then be timestamped to facilitate the reconciliation of certain measurements with the ground speed of the aircraft at the same time and / or the runway area (position of the aircraft) on which the aircraft is traveling at the same time. . These measurements made by the different sensors are transmitted to the determination module 20 which then calculates said local information hoc according to these. According to one embodiment, the local information ibc is directly the state of local track EPIoc estimated by an on-board system of the aircraft from the aforementioned measures. As a variant, the local information i10 is a current braking or deceleration level of the aircraft, for example the current value of its deceleration. By way of illustration, the methods and systems of the applications FR2930669 and FR2978736 can be used for the implementation of the determination module 20. These methods and systems evaluate, in particular, the braking or deceleration performance of the aircraft to estimate a state of running track. For example, the balance of forces makes it possible to obtain the braking force Fb of the aircraft by the following formula: where m is the mass of the aircraft, at the same time acceleration (or deceleration), T engine thrust (for example obtained by the position of the throttle and engine parameters such as the engine speed), Daero aerodynamic drag (for example obtained by modeling from various parameters, by example the angle of incidence, the longitudinal attitude, an output of the airbrakes), Dcenf the resulting drag of a runway contaminant (eg based on a runway profile corresponding to the runway condition EP) and y the slope of the track. The system 1 further comprises a comparator 30 and a feedback loop of this comparator to the brake assist module 10 for the implementation of the invention.

The comparator 30 makes it possible to compare the local information ilec obtained by the module 20 with reference information of the same nature as a function of the reference track state EP. This reference information iref is obtained from a module 15 for obtaining such information, which receives as input the track state EP and / or the braking data, for example the predictive stopping distance D (EP ).

According to one embodiment, the iref obtaining module 15 selects the EP track condition at the input of the brake assist system 10 as reference information iref. In this case, the local information i, oc is the local track state EP, estimated by an on-board system, so that a comparison is possible. In a variant, the iref obtaining module 15 determines a function quantity of EP such that an information representative of a braking or deceleration level of the aircraft, denoted F. It is for example a theoretically achievable deceleration. by the aircraft (in limit of adhesion / friction at the track) on the state of track EP. In this case, the local information ibc is a current braking or deceleration level of the aircraft, so that a comparison is possible.

According to the invention, the comparison by the comparator 30 is intended to determine a possible degradation of the local track state with respect to reference track condition. In other words, it is a matter of testing whether the local track state on which the local information 110 depends is more degraded than the reference track state on which the reference information iref depends.

When the result of the comparison shows that the track condition has not deteriorated since the previous landing, the brake assist system 10 has data (track state EP and stopping distance D (EP) ) that guarantee effective braking. Thus, none of these data of the system 10 is updated, so that the braking setpoint or the alert C (EP) initially generated by the brake assist system 10 from the track condition reference is maintained. On the contrary, when the result of the comparison shows that the track condition has deteriorated, the data of the brake assist system 10 are out of date and no longer guarantee a braking safety. The invention then provides that the reference track state EP or the stopping predictive distance D (EP), as the case may be, is updated according to the determined local information (i1 '), at the level of the brake assist system 10, in order to adapt in real time the braking of the landing to the actual conditions of the track. Indeed, this update makes it possible to provide a brake data (D (EP)) updated at the input of the brake assist module 12, in order to also update the braking setpoint or the warning C ( EP). According to various embodiments, this updating can be carried out either by updating the track state at the input of the brake assist system 10, or by modifying the braking data D (EP) at the output of the stopping distance estimator 11 or input of module 12.

Thus, the flight control system according to the invention comprises: a module 11 for generating a braking data D (EP) as a function of a reference track condition (EP); a braking assistance module 12 receiving as input said braking data generated; a module 20 for determining local information i10 depending on a local track condition (EPIoc) to the aircraft during landing; and a module (10, 30) for updating the reference track state EP or the braking data D (EP) as a function of the determined local information ibc, when the local information i10 informs an Elpio local track condition, more degraded than the reference track state EP, so as to provide an updated braking data D (EP) at the input of the brake assist module. Such a piloting aid system can be integrated in a single computer, or, alternatively, its various functions can be divided between several computers communicating with each other for example to reuse existing computers.

FIG. 2 represents in the form of a logic diagram the main steps of a method of assisting control according to a particular embodiment of the invention. This method can be implemented in a flight control system according to the invention, such as for example described with reference to FIG.

During a step S210, a theoretical track condition or reference EP is received by the aircraft, for example from an aircraft having previously landed or from a ground station. For example, this reference track state EP may be the result of a synthesis of several track conditions obtained during previous landings of several aircraft, this synthesis being carried out by the ground station mentioned above. Then, during a step S220, the brake assist system 10 generates a braking setpoint or a warning message C (EP) as a function of this reference track state EP. This step comprises estimating the predictive stopping distance D (EP) by the estimator 11 as mentioned previously.

The braking setpoint C (EP) can be of different types. This may include applying a certain amount of braking force, a level of depression of the brake pedals, a deceleration level to reach, a stopping distance to reach or a brake pressure. For example, the deceleration level to be achieved can be calculated as an operationally acceptable deceleration level for the aircraft given the reference track condition EP. As a variant, it may be the deceleration level reached by the aircraft in a critical braking condition. The same is true for the stopping distance to be reached: an operationally acceptable stopping distance or, alternatively, a distance minimum stop possible for the aircraft in critical braking condition. The braking conditions are considered critical when the aircraft reaches a braking level limited by the friction of the track or the adhesion to the track. The alert message may be a voice or visual message to the pilot providing brake instructions to apply.

In step S225, the obtaining module 15 provides reference information iref to the comparator 30. As noted above, it may be the EP track condition at the input of the braking assistance system 10 or an information item. representative of a critical braking level or deceleration F deduced from the reference track state EP or from the braking data, here the predictive stopping distance D.

Note that this information representative of a braking or deceleration level may already have been calculated by the brake assist system 10 during step S220, in which case it is directly recovered. Local measurements are performed during a step S230 in order to determine (step S240) a local information ibe characterizing the local track condition EPIC, c or the current level of braking or deceleration F 'of the aircraft during flight. landing (ibc and iref are of the same nature). A current deceleration level may, for example, be obtained directly from an accelerometer. Furthermore, a local track condition can be obtained by the implementation of the mechanisms of the aforementioned documents FR2930669 and FR2978736. The method continues in step S250 where a test consists of comparing the local information i10 determined during the step S240 with the reference information iref of the same nature obtained in the step S225: the state of EP reference track received in step S210 in the case where the local information i10 corresponds to the local track condition EPIoc 15 to the aircraft, the information representative of a braking level or deceleration F determined at step S225 in the case where the local information iloc corresponds to a current level of braking or deceleration F '. The purpose of the S250 test is to determine whether the local information i10, characterizing the area on which the aircraft is landing represents or indicates a track condition that has degraded relative to the theoretical or reference track state EP on which the reference information depends iref- Note that the execution of the test S250 can be conditioned to the determination (S249) of whether the aircraft meets a braking critical condition. For example, the critical braking or deceleration level F (for example theoretical theoretically attainable deceleration at the limit of adhesion to the track) as obtained in step S225 is representative of an extreme level of braking to be achieved (maximum deceleration , minimum stopping distance ...), that is to say obtained in critical braking condition of the aircraft. It is therefore pointless, in this case, to compare this theoretically achievable deceleration with the current braking level of the aircraft if the latter is not in a critical braking situation. By way of illustration, the critical braking conditions resulting from braking limited by the friction of the track are encountered when the difference between a commanded deceleration value of the aircraft and a deceleration value measured by the aircraft exceeds a predetermined threshold. ; the level of manual depression of a brake pedal by an operator (eg pilot) exceeds a predetermined threshold; the difference between a controlled braking level of the aircraft and a measured braking level in the aircraft exceeds a predetermined threshold; or an anti-skid system of the aircraft is triggered. Another example where the condition S249 is implemented is that implementing the mechanisms of the publication FR2930669 referred to above when determining a local track condition ibe in step S240, since this determination is only made in the presence of critical braking conditions of the aircraft. It should be noted that the iref information only being used in step S250, step S225 can be performed at any time of the process between steps S210 and S250, independently of steps S230, S240 and S249 in particular . For example, step S225 can be performed subsequent to the verification of condition S249 in order to avoid an unnecessary calculation of the theoretically achievable deceleration. When the S250 test shows that the track condition has not degraded, the method loops back to step S230. Here, the data used by the system 10 as well as the braking setpoint or the alert C (EP) are not updated. The aircraft thus retains the same braking or warning set because the runway is not further degraded. When the test S250 shows that the track condition has degraded relative to the reference track state, the reference track state EP or the stopping predictive distance D (EP), as the case may be, is updated during a step S260 to take into account the degradation of the runway since the previous landing and thus establish a satisfactory level of braking safety for the landing. Then, the method loops back to step S220 to generate a new braking setpoint or a warning message C (EP) from the updated stopping predictive distance (via the update of EP if necessary).

This loopback allows an update in real time or near real and dynamic of the setpoint or alert during landing. FIG. 3 represents the steps of a method of assisting the piloting of an aircraft, according to a first embodiment of the invention. This method can be implemented in a system according to the invention, as for example described with reference to FIG. 1. During a step S310, similar to the step S210 described with reference to FIG. the aircraft receives an EP reference track condition. During a step S320, similar to the step S220 described with reference to FIG. 2, the piloting assistance system 10 estimates a predictive stopping distance D (EP) from EP and generates an instruction of braking or a warning message C (EP) from D (EP). Step S325 consists of choosing the reference track state EP as reference information ire. Thus, in this embodiment ire = EP as supplied to the input of the comparator 30 for the S350 test. Local measurements are then made during a step S330, as described with reference to Figure 1 and similarly to step S230 of Figure 2. During a step S340, a local track condition EPIoc which constitutes the local information ibc according to the invention is deduced from the measurements made in step S330. For example, refer to documents FR2930669 and FR2978736. During a test step S350 (possibly subject to a condition S349 similar to S249), the comparator 30 compares the local information iloc = Elpio, to the reference information ire = EP to determine whether the track condition has deteriorated. If the two track conditions are equal, for example EP = EPbc = WET (wet track), or if the local track condition, for example EP, oc = DRY (dry track) is less degraded than the track condition reference, for example EP = WET (wet track), the data used by the brake assist system 10 are not modified, and therefore the braking setpoint or the warning C (EP) is also not changed. Steps S330 and following are then reiterated (loopback on S330). If on the other hand the local track condition, for example EPlo, = ICY (icy track), is more degraded than the reference track state, for example EP = WET (wet track), the track condition EP reference (here the reference information iref) 25 is replaced by the local information ibc = EPIoc input braking assistance system 10 during an update step S360. Then the method loops back to step S320 to estimate again D (EP) and generate a new braking or warning setpoint C (EP) from the new updated reference state, in the example after EP update. = i3O = ICY (icy track). The brake assist system 10 is thus reconfigured according to the local track condition determined in step S340. In a variant of the embodiment of FIG. 3, the update step S350 is conditioned on the determination of whether the aircraft encounters a braking critical condition in a manner similar to the step S249 described with reference to FIG. 2. This is the case for example if step S340 implements the mechanisms described in publication FR2930669. FIG. 4a represents the steps of a method of assisting the piloting of an aircraft, according to a second embodiment of the invention.

This method can be implemented in a system according to the invention, as for example described with reference to FIG. 1. During a step S410, similar to step S210 of FIG. 2 and step S310 of Figure 3, the aircraft receives an EP reference track condition. During a step S420, similar to step S220 of FIG. 2 and step S320 of FIG. 3, the pilot assistance system 10 estimates a stop predictive distance D (EP) from EP and generates a brake setpoint or a warning message C (EP) from D (EP). The braking setpoint corresponds for example to the value or level of braking or deceleration operationally acceptable taking into account the reference track state EP. During a step S425, the iref obtaining module 15 determines information representative of a critical or theoretically achievable braking or deceleration level F of said aircraft derived from the reference track state EP or from the stop predictive distance D when the latter is updated as described below. i ref can in particular take the value of the setpoint C (EP) if the latter is actually representative of a braking or deceleration level. Local measurements are made in step S430, similarly to step S230 of Figure 2 and step S330 of Figure 3. In step S440, the braking or deceleration level The current (or effective) F 'of the aircraft is deduced from the local measurements made in step S430, this current braking level F' then constituting the local information ilec representative of the local track condition. The next step S450 is conditioned by the determination S449 of whether the aircraft encounters a critical braking condition in a manner similar to the step S249 described with reference to FIG. 2. When a critical braking condition is encountered by the In aircraft, the test step S450 consists in comparing, by the comparator 30, the local information i10 = F 'with the reference information iref = F, that is to say the level of braking or deceleration that is theoretically achievable. and the current or actual braking or deceleration level to determine if the track condition has degraded.

If the two braking or deceleration levels are equivalent, ie if F '= F ± AF where AF is a tolerance margin, or if the current braking or deceleration level is greater than the braking or deceleration level theoretically achievable, ie F '> F, then this means that the track condition has not deteriorated or has improved since the determination of the reference track state EP , for example during the previous landing. In these two cases, the braking assistance system 10 is not reconfigured and the steps S430 and following are then reiterated (loopback on S430).

If, on the other hand, while the aircraft is in critical braking condition, the current braking or deceleration level F 'is lower than the theoretically achievable braking or deceleration level F, that is to say if F' < F - AF, this means that the track condition has degraded compared to the reference track state EP. According to this embodiment of the invention, the predictive stopping distance to reach D (EP) is then updated to take into account this degradation (in fact, D (EP) increases). To do this, a correction coefficient a (iloc) is calculated during a step S455 as a function of i .10c. For example, the correction coefficient may be a predefined value of x% (x> 100). As a variant, the ratio between the theoretically achievable braking or deceleration level F and the current braking or deceleration level F 'is used as the correction coefficient: a (iloc) = F / F'. Then, in a step S460, the stopping distance D (EP) calculated in step S420 is corrected by the correction coefficient a calculated in step S455: D '(a (iloc); D), for example D '= aD.

The method then loops back to step S420 to generate a new braking setpoint C '(D') from the corrected stopping distance D '(a (iloc); D). Note that the new iteration of step S425 will then determine iref = F from this new corrected stopping distance D '(a (iloc); D), and not from EP which is not directly set to in this embodiment (D 'corrected implicitly indicates a modification of EP). FIG. 4b represents the steps of a method of assisting the piloting of an aircraft, according to a variant of the second embodiment of the invention described with reference to FIG. 4a. This embodiment differs from Figure 4a in that, when a degradation of the track is detected while the aircraft meets critical braking conditions (thanks to the S449 and S450 tests) and the predictive stopping distance to to reach D (EP) must then be updated, instead of calculating a correction coefficient a (step S455) and correcting (steps S460) this stopping distance D (EP) with this correction coefficient a, a new stopping distance D "is calculated by interpolation during a step S465 A new braking setpoint C" (D ") is then calculated during a new step S420 from this new stopping distance D as previously described for the new iteration of step S420 of Figure 4a. More precisely, the new stopping distance D "is calculated by interpolation of several minimum stopping distances di representative of theoretical track states and with which respective theoretical braking or deceleration levels are associated, by way of nonlimiting example. a correspondence table between these theoretical braking or deceleration levels and these theoretical stopping distances (for example associated with each possible theoretical track state) can be used, thus when the current or actual braking or deceleration level is used. F 'is situated between the theoretical braking or deceleration levels fi and fi, respectively corresponding to the stopping distances di and di + 1, the new stopping distance D "is calculated by applying an interpolation function INTERP to these theoretical stopping distances: D "= INTERP (di; di.1), for example by linear interpolation For example, if the braking level o u current deceleration is located at z% of the braking or deceleration level associated with the distance di and at (100-z)% of the braking or deceleration level associated with the distance di + 1, then the stopping distance D "could be obtained by the formula: D "= z% * di + (100-z) edi + 1. Figure 5 is a graphic illustration of the evolution of stopping distance and braking level in an operational landing scenario using the invention. This scenario can in particular implement the embodiment of FIG. 3, where the piloting assistance method is based on the comparison of the reference track state EP with an estimated local track condition EPIoc. In this scenario, an aircraft equipped with a flight control system according to the invention, such as that described with reference to FIG. 1, is approaching a track theoretically covered with snow (EP = COMPACTED SNOW). . The braking assistance system 10 takes into account this track state 35 EP and calculates a braking or warning setpoint C (EP = COMPACTED SNOW) implemented by a braking or restitution device once on the ground during phase 1. This braking or warning setpoint is based on a stopping distance D (EP = COMPACTED SNOW). During phase 1, the actual or local track state estimated in step S340 is more degraded than mentioned by the iref information, of the SNOW type for example. However, the critical braking conditions are not detected in the S249 test. The update S260 / S360 of the track state EP or the distance D (EP), and consequently of the braking or deceleration or warning set point C (EP), is therefore not performed.

From phase 2, the critical braking conditions are met (test S249). Local measurements of the braking or deceleration level (making it possible to determine ibc) thus make it possible to detect a degradation of the track. Indeed, during step S340, the effective level or braking current F 'is much lower than the braking or deceleration level theoretically achievable under critical braking conditions iref = F (see Figure 5c in phase 1). A degraded local track state is thus obtained at the end of step S340. The track state EP or the predictive stop distance D (EP) is then updated according to the estimated local track state EPlec or F ', then applied in real time or near real time by the braking assistance system during a phase 2 to generate a new braking or warning set C (EP). For example, a braking monitoring device (ROP) adapts its alerts and a braking control device (BTV) controls a deceleration adapted to the conditions encountered, to avoid the risk of slippage. The predictive stopping distance is increased, this time corresponding to a SNOW track condition (see Figure 5a).

However, during Phase 2, the runway condition deteriorates again to ICY type as the aircraft encounters an icy area. Local measurements of the braking or deceleration level (allowing .10, determine i10) make it possible to detect this degradation of the runway (EP, ', from SNOW to ICY), in particular because the aircraft is still confronted with critical conditions of braking. The effective level of braking or deceleration F 'is much lower than the deceleration braking level theoretically attainable F obtained from the previously updated reference information iref (see Figure 5c at the end of phase 2). The track state EP or the predictive stop distance D (EP) is then updated according to the new estimated local track state EP, 'or F' and then applied in real time or near real-time by the braking assistance system during a phase 3 to generate a new brake or warning setpoint C (EP). Likewise, the corresponding predictive stopping distance D (EP) is increased (see Figure 5a). Local measurements then make it possible to observe a new change of runway condition, this time inducing an improvement of the runway conditions (see Figure 5c, phase 4). This time, the track state EP or the predictive stop distance D (EP), and therefore the braking setpoint, are not updated, and are maintained (phase 4) as in phase 3. The examples above are only embodiments of the invention which is not limited thereto.

Claims (3)

REVENDICATIONS1. Method for assisting the piloting of an aircraft during the landing phase, comprising a step of generating (S220, S320, S420) a braking data item (D (EP)) as a function of a reference track state (EP), said braking data being inputted to a brake assist module (12), the method being characterized by the following steps: - determining (S240; S340; S440) local information (ilm ) function of a local runway condition (EPloc) to the aircraft upon landing; and updating (S260; S360; S455, S460; S465) the reference track state (EP) or the braking data (D (EP)) according to the determined local information (i10c) when the local information (ik, c) indicates a local track condition (EPI, 'c) more degraded than the reference track condition (EP), so as to provide a braking data (D ( EP)) updated at the input of the brake assist module (12). The method of claim 1, wherein the local information (ibc) is an estimate of the local runway condition (EPloc) by a system embedded in the aircraft, and the updating step (S260; S360) updates the reference track state (EP) by the estimated local track condition (EPioc). 3. Method according to claim 1, wherein the local information (ibc) is representative of a current level of braking or deceleration (F ') of said aircraft, and the method comprises a step of obtaining (S225; S425) d a reference information (iref) representative of a braking or deceleration level (F) of said aircraft derived from the reference track state (EP) or the braking data (D (EP)), and a step of comparing (S250; S450) the reference information (iref) with the local information (ihm) to determine if the local track state (EP10) is more degraded than the reference track state (EP). A method according to claim 2 or 3, wherein the updating step (S260; S360; S455, S460; S465) is performed when at least one of the following critical conditions is encountered: the difference between a commanded deceleration value the aircraft and a deceleration value measured by the aircraft exceeds a predetermined threshold; the level of manual depression of a brake pedal by an operator exceeds a predetermined threshold; the difference between a controlled braking level of the aircraft and a measured braking level in the aircraft exceeds a predetermined threshold; an anti-skid system of the aircraft is triggered. The method according to claim 3, wherein the updating step comprises calculating (S455) a correction coefficient (a) dependent on the determined local information (ibc) and the correction (S460) of the braking data (D (EP)) as a function of the calculated correction coefficient (a). The method of any one of claims 1 to 4, wherein the braking data is a minimum stopping distance (D) dependent on the reference track condition (EP), and the stopping step day includes the correction (S465) of the minimum stopping distance from the determined local information (ibc), by interpolation of several minimum stopping distances (di) respectively associated with theoretical track states. 7. Method according to claim 6, wherein the determined local information (ii oc, 1 is representative of a current level of braking or deceleration (F ') v of said aircraft, and the correction (S465) of the minimum distance d stopping from the determined local information (i10) comprises the interpolation of minimum stopping distances (d1) associated with theoretical braking or deceleration levels as a function of the determined current braking or deceleration level (F '). 8. System (1) for assisting the piloting of an aircraft during the landing phase, comprising: - a module (11) for generating a braking data (D (EP)) as a function of a state of reference track (EP); a braking assistance module (12) receiving as input said braking data generated; a determination module (20) for local information (i10) which is a function of a state of local runway (Elpioc) to the aircraft during landing, and - an update module (10, 30) of the reference track state (EP) or braking data (D (EP)) as a function of the determined local information (iloc), when the local information (i3O) informs a localized runway condition (EPloc) more degraded than the reference runway condition (EP), so as to provide updated brake data (D (EP)) at the input of the brake assist module .9. The system (1) of claim 8, wherein the local information (i10) is an estimate of the local track state (EP10), and the update module (10, 30) is configured to update the reference runway condition (EP) by the estimated local runway condition (EP - ioc) - 10. The system (1) according to claim 8, wherein the local information (i10) is representative of a level braking current or deceleration (F ') of said aircraft, and the system (1) comprises a module (15) for obtaining information, called reference (iref), representative of a braking or deceleration level (F ) of said aircraft derived from the reference runway condition (EP) or the braking data (D (EP)), and a comparator (30) of the reference information (iref) with the local information (i10 ) to determine if the local track condition (EP10) is more degraded than the reference track condition (EP). 11. System (1) according to claim 10, comprising a module for determining whether at least one of the following critical conditions is encountered in order to trigger an update by the update module (10, 30): the difference between a controlled deceleration value of the aircraft and a deceleration value measured by the aircraft exceeds a predetermined threshold; the level of manual depression of a brake pedal by an operator exceeds a predetermined threshold; the difference between a controlled braking level of the aircraft and a measured braking level in the aircraft exceeds a predetermined threshold; an anti-skid system of the aircraft is triggered. Aircraft comprising at least one flight control system (1) according to one of claims 8 to 11.